You wouldn't go in the Herpetarium if you weren't in search of a thrill. Something to make your skin crawl. When a pile of Gila monsters lying next to their own recently shed skin fails to do it for ya, try Missouri's own Ozark hellbender. The weird, primitive look of this harmless salamander elicits an eeewwww from just about everyone who passes its small tank. Its irregularly oblong shape and mottled skin mimic the stream-worn rocks where the hellbender makes its home. Only the opening and closing of its toothless mouth assure you that yes, that end is the head. Upon close inspection, you'll find its tiny blind-looking eyes. A bit gross, yes, but intriguing too. It's the heftiest salamander in North America, a relative of the giant salamanders of China and Japan. An evolutionary relic, it retains some primitive traits breathing through its skin and laying eggs to be fertilized in the open, as fish do. You might never see one in the wild, though; its numbers are dwindling. The hellbender has disappeared from the Spring River in Arkansas, says Stan Trauth, zoology professor at Arkansas State. As for the name, Trauth says he's not satisfied with any of the various theories about its origin. Seems the story of the hellbender, like our slimy friend himself, remains obscure.